1. Field of the Invention
This invention relates to the manufacture of slotted beam contact elements for an electrical connector, and, more particularly, to the manufacture of insulation-penetrating, bifurcated beam contact elements from a metallic strip in which the furcations of the beam are formed in a manner which permits controlled processing of portions of the strip which are destined to form the surfaces of the furcations that engage a conductor.
2. Prior Art
In the telephone industry where it becomes necessary to interconnect seemingly countless numbers of insulated conductors, a solderless, slotted beam type electrical connector is widely used. This type of connector generally includes an electrically conductive element, which is commonly referred to as a slotted beam contact element and which comprises a base portion having a beam extending from opposite sides thereof with each of the beams bifurcated to form a slot for receiving an insulated conductor. See, for example, U.S. Pat. No. 3,027,536, issued Mar. 27, 1962, to J. P. Pasternak. The spacing between the furcations of each beam is such that opposing surfaces thereof which define the slot penetrate the insulation of an insulated conductor which is moved into the slot to establish electrical engagement between the conductor and the furcations. Because of the resiliency of the bifurcated portions of the beam, they tend to move toward each other after a conductor has been moved into the slot to clamp the conductor tightly.
In the prior art, slotted beam contact elements have been formed along a strip of metal by the step of punching the strip to form central base portions having beams extending bilaterally thereof. For those connectors destined to be used in systems in which conductors are frequently moved into and out of the connectors (see for example, U.S. Pat. Nos. 3,112,147 issued Nov. 26, 1963 to W. Pferd et al., and 3,798,587 issued Mar. 19, 1974 to B. C. Ellis, Jr., et al.), each beam is lanced to bifurcate the beam with opposing lanced surfaces of the furcations defining a conductor-receiving slot. The step of lancing to bifurcate each beam invariably moves one of the furcations out of the plane of the contact element thereby impairing the connection process when a conductor is moved into the slot. Also, the step of lancing the beams to form the furcations in their final position makes it difficult to control the shape of the opposing lanced surfaces of the furcations which define the slot, and forms burrs on the lanced surfaces which deform a conductor that is moved into the slot. For those connectors which are to be used in systems in which connections are not made repeatedly (see, for example, U.S. Pat. No. 3,858,158 issued on Dec. 31, 1974 in the names of R. W. Henn et al.), each conductor-receiving slot is formed by the punching of a narrow slot in a beam; however, difficulties have been encountered in punching narrow width slots through relatively thick strips of metal.
Since the conductors which are connected with insulation-penetrating slotted beam contact elements are used in a variety of systems where they are exposed to a wide range of temperature conditions and/or physical abuse such as, for example, wind loading in outside plant systems or solder heat in central offices, the conductors are insulated with different materials which are capable of withstanding particular conditions. Rather than manufacture different kinds of slotted beam contact elements which are usable with different types of insulation, it is more economical to manufacture a contact element which is capable of tearing, penetrating or slicing through a variety of types of insulation to establish an electrical connection and which is capable of maintaining a tight connection over a period of time. This is accomplished by shaping the opposing surfaces of the bifurcated beam portions to a predetermined configuration; however, as noted hereinbefore, the satisfactory shaping of these surfaces has not been possible when the furcations are formed by the step of lancing or by the forming of a narrow slot in the beam.
Also, it may be important that selected surfaces of these kinds of contact elements be plated with a corrosion-resistant material such as, for example, gold or solder. In contact elements of the type shown in U.S. Pat. No. 3,858,158 the narrow slot punched out in each beam facilitates, to a limited extent, the plating of the opposing walls of the furcations which define the slot, while in U.S. Pat. No. 3,394,454 issued July 30, 1968 in the name of A. Logan, portions of the inner edge surfaces of the conductor-receiving slot are coined to space apart the bifurcated portions and to facilitate the plating of the edge surfaces. However, the use of coining to space apart the furcations is not altogether satisfactory because of the control required to achieve the final slot width required for a suitable electrical connection with a conductor.
Although the prior art discloses contact elements having opposing jaw portions which are moved toward each other to engage a conductor (see, for example, U.S. Pat. No. 3,259,873), it is not desirable to close the bifurcated portions of a connector, which is mounted in a plastic housing, upon a conductor after it has been inserted between the bifurcated portions. Also, because of the possibility of unwanted metal flow, it is not desirable to shape the opposing faces of the slot walls after the furcations have been formed (see, for example, U.S. Pat. No. 3,587,502), unless elaborate physical restraints are imposed. It is much more desirable to be able to manufacture a slotted beam connector with the slot pre-sized to receive the conductor and with the walls of the slot processed prior to the formation of the furcations.